An analysis of cohabiting couples showed a rise from 3 per cent of single women cohabiting in 1979 to 26 per cent in 1989. The proportion of births outside marriage rose from 8 per cent in 1970 to 12 per cent in 1980 and 30 per cent in 1991.
The survey showed one in six cohabiting couples have never married but are living with dependent children. These families tend to live on lower incomes and miss out on legal rights they would enjoy if they were married.
Nearly one in four had family incomes below pounds 100, compared with one in 16 married couples with children.
The study, sponsored by the Joseph Rowntree Foundation, was conducted by Kathleen Kiernan, now at the London School of Economics, and Valerie Estaugh of the Family Policies Study Centre.
Ms Kiernan said: 'It has been evident for some years that a growing number of couples are starting their families outside marriage. What has not been so apparent is that the cohabiting partners who do this are disproportionately socially and economically disadvantaged.'Reuse content